3-D Finite Element Models And Parameter Analysis Of Endoskeletal Trans-tibial Monolimb

Monolimb is a new type of lower-limb prostheses, which is made of macromolecule polymer. The socket and prosthetic shank of monolimb are integrative. Compared with traditional prosthesis, monolimb is more economical, good-looking and portable, so it is worth researching. But monolimb is only an idea now, and it has not been largely applied to clinic. Recently some scholars and institutions started to apply themselves to researching monolimbs, but their researches aimed at manufacture and materials, and have not involved stress analysis of monolimbs. Because of the difference in structure between monolimbs and traditional prostheses, it is necessary to execute stress analysis of monolimbs.The purpose of this research was to establish a series of 3D models of trans-tibial monolimbs. By use of finite element analysis on these models, the stress analysis and parameter analysis ware obtained. This research include:The uniform wall thickness of the model based on real geometry shape of a trans-tibial monolimb for experiments is three millimeters. The soft tissue and bone of stump were considered. The model was applied to the load corresponding to the subphase of the stance of Heel Off. Using a finite element solver, the quasi-static stress distribution within the model was obtained.Using thicker wall thickness, three 3D finite element models with different wall thickness were established. The material properties, stump shape, bone orientationand load were same. Through finite element analysis, the influence of wall thickness to the stress distribution within the models was gained.Various material properties were given to the model, such as polypropylene homopolymer, polypropylene with 20% glass fiber, acrylics, and polypropylene and polyethylene copolymer. Without change of other conditions, through finite element analysis, the stress distributions with various materials were obtained.The model was applied to the loads corresponding to the subphase of the stance of Heel Strike, Foot Flat, Mid-Stance, Heel Off and Toe Off. Using a finite element solver, the characteristics of the stress distribution corresponding to each subphase of stance were analyzed.The moment of inertia of each model was computed. The influence of mass distribution to moment of inertia was analyzed, thus the rationality of monolimb design was fed back in sport control.A model of traditional prosthesis with the same socket shape of the monolimb was established. The stress distributions within socket and stump were analyzed. Compared with the results of the monolimb model, stress damping of monolimb was discussed.This research is the first finite element stress analysis to monolimbs, which provide the basis for CAE of monolimb. And it's also the first time to analyze wall thickness which is an important parameter in designing monolimb, and to introduce moment of inertia as a parameter in designing monolimb. So it will be valuable in both academic research and clinical practice.